The subject matter of this disclosure relates generally to multi-resonant LED drivers, and more particularly, to a system and method for achieving precise regulation of multiple outputs in a multi-resonant light emitting diode (LED) driver stage.
Multi-resonant converters and variants thereof are a very efficient means for controlling a wide range of currents through an LED load. FIG. 1 is a schematic diagram illustrating a basic LED drive 10 that is implemented with a multi-resonant variant converter 12. The LED drive 10 can drive a single string of LEDs, or series-parallel arrangements of LEDs that are represented in FIG. 1 by a single diode (D1) 14. The single diode 14 can be replaced by a string of LEDs in series or by series parallel arrangements of LEDs. The LED current 15 is usually sensed with a sense transformer placed at a current sense point 16 on the secondary side of the multi-resonant converter 12. The main isolation transformer 18 is represented as element T1 in FIG. 1. Although such converters may be useful to provide precise regulation through a load, known multi-resonant converters and their variants are not capable of providing precise regulation of multiple outputs such as required for multi-stringed LEDs without sacrificing efficiency or the undesirable addition of a significant number of parts.
FIG. 2 is a simplified schematic diagram illustrating a basic half bridge resonant converter 100 with a multi-resonant drive 102. The half bridge resonant converter 100 can drive a single string of LEDs, or series-parallel arrangements of LEDs that are represented in FIG. 2 by a single diode 104. The single diode 104 can be replaced by a string of LEDs in series or by series parallel arrangements of LEDs. The LED current is usually sensed with a sense transformer placed at a current sense point on the secondary side of the multi-resonant drive 102. Although such converters may be useful to provide precise regulation through a load, these known multi-resonant converters and their variants are not capable of providing precise regulation of multiple outputs such as required for multi-stringed LEDs without sacrificing efficiency or the undesirable addition of a significant number of parts, as stated herein.
Mixed light systems, such as blue mixed with red LEDs, often require precise control over a second output while maintaining control of the first output. It would be beneficial and advantageous to provide a system and method that employs a multi-resonant converter in which a second output can be regulated without sacrificing the efficiency of the overall power train.